1. Field of The Invention
This invention generally relates to gas sorption compositions, apparatus, and associated processes, for effecting the sorptive removal of hazardous gases containing Group II-VII elements of the Periodic Table, such as are widely encountered in the manufacture of semiconducting materials and semiconductor devices.
2. Description of The Related Art
In the manufacture of semiconducting materials and semiconducting devices, a wide variety of hazardous gases are employed or produced, which comprise compounds containing elements from Groups II-VII of the Periodic Table. As used in such context, the term "gases" will be understood to include vapors as well as gases.
The aforementioned hazardous gases may derive from organometallic source reagents employed as precursor materials for the deposition of elemental metals on the semiconductor substrate, as for example by chemical vapor deposition (CVD) techniques. Other hazardous gases are employed in cleaning semiconductor manufacturing equipment such as reactor tubes and susceptors, and/or as etchants for the manufacture of microcircuitry devices.
An illustrative listing of hazardous gas compounds which contain Group II-VII constituent elements and are commonly encountered in the semiconductor industry is set out below.
Group II:
Organic compounds of beryllium, magnesium, zinc, cadmium, and mercury. PA1 Organic compounds of aluminum, gallium, and indium; hydrides of boron. PA1 Silane, and chlorosilanes (SiH.sub.4-x Cl.sub.x, wherein x is an integer whose value is 1 to 4 inclusive); germane; and certain fluorinated etching agents and products. PA1 Hydrides of nitrogen, phosphorus, and arsenic; alkyl arsine and alkyl phosphine compounds. PA1 Hydrides of sulfur, selenium, and tellurium; alkyl selenium and alkyl tellurium compounds. PA1 Hydrogen halides (fluoride, chloride, bromide, and iodide). PA1 (1) carbanions whose corresponding protonated compounds have a pK.sub.a value of from about 22 to about 36; and PA1 (2) anions formed by reaction of the carbanions with the primary component of the mixture.
Group III:
Group IV:
Group V:
Group VI:
Group VII:
The aforementioned gaseous compounds occur in widely varying concentrations in semiconductor manufacturing plants, as constituents of vent gases and effluent streams, which due to the hazardous character of these gaseous compounds must be treated to remove such compounds so that they are not released into the environment.
As a result of the foregoing toxicity and safety considerations, considerable effort has been expended in developing compositions and treatment systems for removing such hazardous gaseous compounds and their constituent Group II-VII elements from gaseous effluents which are discharged by semiconductor manufacturing facilities. See, for example, Y. Abe and H. Sugiyama, "Treatments of Semiconductor Manufacturing Plant Exhaust Gases," PPM, 16[6], 40-52 (1985); L. L. Eiger, "Toxic Gas Monitoring for Chemical Vapor Deposition Process Systems," presented at STEP/SEMI Technical Education Programs "Safety Aspects of Effluents From CVD Process Systems," May 23, 1986; E. Flaherty and R. P. Brook man, "Treatments of Gaseous Effluent from Semiconductor Plants," presented at STEP/SEMI Technical Education Programs "Safety Aspects of Effluents From CVD Process Systems," May 23, 1986; and C. Mistry, Y. Ohno, and T. Urata, "Process in Semiconductor Process Exhaust Gas Treatment Technology in Japan," presented at STEP/SEMI Technical Education Programs "Safety Aspects of Effluents From CVD Process Systems," May 23, 1986.
Among the treatment technologies that have come into usage for removal of Group II-VII elements and compounds from semiconductor plant gaseous effluents are combustion, chemical oxidation, and activated carbon treatment of the effluent streams. Each of these treatment methodologies is discussed in turn below.
In the combustion treatment of semiconductor manufacturing effluent gases, "burn boxes" frequently are employed to achieve substantially complete oxidation of the hazardous gases in the effluents. The resulting oxidized products in the combusted effluent gas stream then are trapped by aqueous scrubbing of the gas stream. Such combustion treatment has the significant disadvantage that large volumes of relatively dilute liquid and solid wastes are produced, as combustion by-products. Further, such combustion is very costly, particularly for small-scale semiconductor manufacturing operations.
Chemical oxidation also has been employed to treat semiconductor plant gaseous effluent streams containing Group II-VII constituents, utilizing aqueous oxidizing agents such as acidic potassium permanganate (KMnO.sub.4) and sodium hypochlorite, to oxidize arsine, phosphine, silane, and diborane, to yield water soluble materials or precipitates. This treatment methodology also suffers the disadvantage of generating large volumes of dilute waste by-products. In addition, since substantial energy is released in these chemical oxidation reactions, explosive conditions can be created, thereby posing a serious risk of damage and injury in the semiconductor manufacturing plant.
The use of activated carbon beds to physically sorb hazardous Group II-VII constituents from semiconductor manufacturing effluent gas streams is well established (see, for example, F. Ito, M. Kobayashi, T. Abe, "Waste Gas Detoxification," Japanese Kokai Tokkyo Koho JP 61/118117A2 [86/118117], June 5, 1986; M. Sugiyam, S. Kudo, H. Okinori, "Agents for Removing Arsenic Compounds," Japanese Kokai Tokkyo Koho JP 60/238144 A2 [85/238144], Nov. 27, 1985; V. M. Bogdanov, Yu. I. Shumyatskii, O. V. Moiseichuk, Z. A. Suchkova, S. P. Neshumova, V. V. Fedorovskaya, G. I. Chugunova, "Removal of Impurities of Phosphine and Arsine from Gases," U.S.S.R. SU 1181692 A1, Sept. 30, 1985; and Calgon Carbon Corporation, "Ventsorb.RTM. for Industrial Air Purification," Bulletin 23-56b-1986).
Nonetheless, activated carbon treatment in such application suffers the disadvantage that the sorptive affinity of activated carbon for the Group II-VII hazardous gas constituents of the semiconductor manufacturing effluent streams is generally relatively low, under normal effluent process (temperature, pressure) conditions. As a result, very large volumes of activated carbon are required to effectively remove the hazardous gas components, in order to achieve concentrations of such hazardous components in the treated gaseous effluent which are below their Threshold Limit Values (TLV).
To meet TLV effluent standards, then, it frequently is necessary to provide massive beds of activated carbon which, in addition to the considerable capital equipment and operating costs associated therewith, are difficult to effectively control and regenerate for optimum usage of the sorbent material.
In prior copending U.S. patent application Ser. No. 07/163,792 filed Mar. 3, 1988 and prior issued U.S. Pat. No. 4,761,395, the disclosures of which hereby are incorporated by reference herein, there is disclosed a scavenger composition having utility for purifying a gaseous mixture comprising (i) a primary component selected from one or more members of the group consisting of arsine, phosphine, ammonia, and inert gases, and (ii) impurities selected from one or more members of the group consisting of Lewis acids and oxidants. This scavenger composition comprises a support having associated therewith, but not covalently bonded thereto, an anion which is reactive to effect the removal of the impurities from the gaseous mixture, the anion being selected from one or more members of the group consisting of:
There is a continuing need in the art for improved technology to remove hazardous gases containing Group II-VII constituents, as produced in the manufacture of semiconductor materials and devices. Such need is particularly acute in instances where concentrated reagent gases may be released into the ambient environment as a result of reagent container and/or flow circuitry failure.
An example is the situation arising when a gas cylinder of a reagent such as arsine is connected to a manifold by a regulator which is defective, or in use breaks down, resulting in leakage of arsine to the surrounding air. For such instances, there has not been developed any suitable means of "quenching" the arsine leak in any safe and effective manner. Instead, semiconductor manufacturing workers have been forced to don protective apparel and breathing devices and to place the defective regulator and cylinder unit in an exterior environment, for dilution by and dispersal to the ambient atmosphere, and/or in a bath of aqueous potassium permanganate solution. These expedients are highly undesirable. Ambient air discharge may create health and safety concerns as well as constitute air pollution activity which may be violative of legislative or regulatory constraints on hazardous material emissions. Bulk potassium permanganate contacting i also undesirable, due to the resulting highly exothermic reaction of the arsine with potassium permanganate, and the potential for explosion.
It would therefore be a substantial advance in the art to provide gas sorption compositions which may be usefully employed to efficiently remove Group II-VII gaseous constituents produced in semiconductor manufacturing operations, both in bulk quantities at high concentrations, as well as at lower concentrations from gas mixtures containing such Group II-VII constituents.
Accordingly, it is an object of the present invention to provide improved compositions useful for treating gases which are employed and/or generated in semiconductor manufacturing operations, comprising Group II-VII constituents.
It is another object of the invention to provide improved process technology for treating such semiconductor manufacturing gases by contact thereof with such compositions.
It is a further object of the present invention to provide improved apparatus for treatment of semiconductor manufacturing gases, to remove Group II-VII constituents therefrom, thereby yielding gases depleted in such constituents for discharge as final effluent from the semiconductor manufacturing process system.
It is a still further object of the present invention to provide apparatus for achieving rapid, safe, and substantially complete removal of bulk leakages or other gross volumes of Group II-VII gaseous compounds at high concentrations.
Other objects and advantages of the present invention will be more apparent from the ensuing disclosure and the appended claims.